1. Field of the Invention
The invention relates to network device maintenance and more specifically to propagating failure information to network transponders.
2. Description of the Related Art
Optical networks can be used to connect subscribers of telecommunication services to telecommunication service providers. The communication link between a subscriber and a service provider is typically created by connecting an end node at the subscriber's location to an end node at a service provider's location, via a communication line, such as a fiber optic cable. FIG. 9 is an example of a typical optical network that can be used to connect subscribers of telecommunication services to telecommunication service providers. One end node, such as end node 910 could be located at the subscriber's location, and another end node, such as end node 920, could be located at the service provider's location.
Because a subscriber's location and a service provider's location can be separated by long distances, the communication signal may degrade as it passes through the communication line. To overcome signal degradation, regeneration nodes, such as regeneration node 900, can be positioned between the end nodes. Regeneration nodes can overcome signal degradation by generating a new signal based on the signal received via the communication line, and propagating the new signal through the network.
End nodes and regeneration nodes include optical transponders for sending and receiving optical signals. Each transponder typically has port optical interfaces and line optical interfaces, each interface having lasers used for sending optical signals. To decrease unnecessary energy usage and reduce unnecessary safety risks, optical transponders can be configured to shut off a laser if a network failure is detected. In particular, a transponder does not distinguish between a network failure detected at a port interface versus those detected at a line interface, and thus they do not take specific actions based on any such distinctions.
FIG. 9 shows the propagation of a network failure through a network in accordance with prior art. Transponders 901, 905, 911, and 921 are configured to generate an alarm signal and shut off a laser if a network failure is detected at a communication interface. Transponder 911 detects a network failure at port optical interface 913 and responds by generating an alarm signal. Transponder 911 then shuts off the laser of line optical interface 912.
Once the laser of line optical interface 912 is shut off, transponder 911 no longer sends signals from line optical interface 912, and network failure 915 occurs. Transponder 901 then detects network failure 915, generates an alarm signal, and shuts off the laser of port optical interface 903, thereby creating network failure 904. Transponder 905 then detects network failure 904, generates an alarm signal, and shuts off the laser of line optical interface 906, thereby creating network failure 908. Finally, transponder 921 detects network failure 908, generates an alarm signal, and shuts off the laser of port optical interface 923, thereby creating network failure 924. In this manner, a network failure is propagated through the network.
The alarm signals generated by the transponders are detected by a network management application used by the service provider to monitor and manage the network. In the previous example, the network management application would detect multiple alarm signals for the propagation of a single network failure through the network.
A problem with the laser shut off action performed in the prior art is the additional management overhead created by processing redundant alarm signals and reactivating multiple lasers, for a single network failure. Also, in the prior art the transponders do not distinguish between network failures detected at a port interface versus those detected at a line interface, and thus they do not take specific actions based on any such distinctions.
There exists a need, therefore, for an improved technique for responding to network failures, that reduces both the number of alarm signals that are generated and the number of laser shut off actions that are effected in response to the failures.